Hello,
Could you explain in more detail what solution you are trying to achieve?
Because purpose of failover function is to have continuous connection to internet, if yours main WAN is not available it switches to backup and when main WAN connection recovers it switches back to main, that is it. If you want to switch between them manually, then failover should be disabled, because it will always prefer main WAN connection.
The option you mentioned is used to execute commands like turning on or off output, or changing profile, if you would want to employ some kind of warning if main line is down or apply some kind of data limits.
Best regards,
VidasKac.